The present embodiments relate generally to advanced composites and, more particularly, to systems and methods for forming reinforced composite materials. The present embodiments are related to U.S. Pat. No. 6,607,626, issued Aug. 19, 2003; U.S. Pat. No. 6,939,423, issued Sep. 6, 2005; U.S. Pat. No. 7,235,149, issued Jun. 26, 2007; U.S. Pat. No. 8,007,894, issued Aug. 20, 2011; U.S. Pat. No. 8,048,253, issued Nov. 1, 2011; and U.S. Pat. No. 8,168,029, issued May 2, 2012, all of which are herein incorporated by reference in their entirety.
Advanced composite materials are increasingly used in high-performance structural products that require low weight and high strength and/or stiffness. Composite materials are engineered materials that comprise two or more components. Polymer composites may combine reinforcing fibers such as carbon fiber, glass fiber, or other reinforcing fibers with a thermosetting or thermoplastic polymer resin such as epoxy, nylon, polyester, polypropylene, or other resins. The fibers typically provide the stiffness and strength along the direction of the fiber length, and the resin provides shape and toughness and acts to transfer load between and among the fibers. The structural performance of an advanced composite part may increase with increased fiber-to-resin ratio (also called fiber volume fraction), increased fiber length, closer alignment of fiber orientation and the load path through the part (in contrast to random fiber orientation), and the straightness of the fibers. The weight of an advanced composite part can also be optimized by selectively adding or subtracting material according to where it is highly and lightly stressed.
Typically, the manufacture of high-performance, advanced composite parts is a slow and labor-intensive process. Thus, several approaches for automating the fabrication of advanced composite parts have been developed to reduce hand labor, decrease cycle time, and improve part quality and repeatability. Such machines are used to fabricate small and large parts ranging from aircraft fuselages and internal structural members to pressure vessels, pipes, blades for wind turbines, and wing skins. For thermoplastic applications, these machines typically place tape material directly on a mandrel or a mold using a material placement head mounted on a multi-axis numerically controlled machine. As the material is laid up, it is consolidated with any underlying layers. This is called “in situ” consolidation.
A different approach, described in U.S. Pat. Nos. 6,607,626 and 6,939,423, which are herein incorporated by reference, is to lay up a substantially flat “tailored blank” where all the plies of the composite laminate are only tacked together. Once the tailored blank has been made, subsequent processing steps are used to consolidate the plies together and form the blank into its final shape.
Forming tailored blanks into desired parts can be challenging, especially when the parts must accommodate significant structural loads. For example, composite components must often meet design specifications that include high vertical loads. In cases where the high compressive loads pass through bends and corners of a composite part, high out-of-plane loads can exist that limit the strength to far below the actual compressive strength of the composite material. One such type of structure is a stringer. Typical thermoformed or stamp-formed composite stringers, for example, are excellent in axial and bending loads, but suboptimal for concentrated vertical or “z-direction” compression loads. As vertical compression loads transfer around the radii of a stringer, the stringer radii will typically crush or yield well below the stringer web strength capability and additional local reinforcement may be required to meet load requirements.
There remains a need for systems and methods for rapidly producing advanced composite parts with corners of sufficient compressive strength and without an excessive number of plies.